The central probe agency said it has issued a provisional order for attachment of the assets, under the Prevention of Money Laundering Act (PMLA), and seized a Rs 810 million valued penthouse (created by joining three flats) and a flat worth Rs 15.45 crore in the sea-facing Samudra Mahal apartments in the Worli area of Mumbai.

"21 immovable properties of Nirav Modi and companies controlled by him, with a market value of Rs 5.23 billion, have been provisionally attached.

"These include 6 residential properties, ten office premises, 2 flats in Pune, a solar power plant, a farmhouse in Alibaug and 135 acres of land in Karjat in Ahmednagar district," the agency said.

While the agency had earlier seized gems, diamonds, jewellery, shares, bank deposits and costly cars in this case since it registered a criminal case under PMLA on February 14, this is the first major action to seize immovable assets.

While the Samudra Mahal properties and two other flats in Punes Hadapsar area are in the name of Modi and his wife Ami, the assets attached in the pricey Kalaghoda and Opera House area in the Maharashtra capital are in the name of Modi's diamond firm-- Firestarter Diamond International Private Limited.

A farmhouse and adjoining land, worth over Rs 427 million, in the Kihim area of beach-side Alibaug of the Nirav Modi Trust has also been attached.

Similarly, a 53-acre solar power plant, valued at Rs 700 million, in the Karjat area of Ahmednagar district of the state has also been brought under the same action.

Modi, Choksi and others are being investigated by the ED and other probe agencies after the fraud recently came to light, following a complaint by the Punjab National Bank that they allegedly cheated the nationalised bank to the tune of Rs 114 billion, with the purported involvement of a few employees of the bank.

The CBI and the ED have registered two FIRs each to probe the case. Both Modi and Choski are said to have left the country before criminal cases were lodged against them.